Naturally occurring clays such as dioctahedral smectites are composed of semicrystalline aluminosilicate layers (lamellae) held together by Van der Waals and electrostatic forces. Anionic charges on the siliceous layers are neutralized by cations in the interlamellar spaces. These cations are usually sodium, calcium, or potassium. When these cations are large oligomers of inorganic cations such as Fe.sup.+3, Cr.sup.+3 or when they are metal hydroxy polymer cations such as (Al.sub.13 O.sub.4 (OH).sub.24 (H.sub.2 O).sub.12).sup.7+ or (Zr(OH).sub.2.4H.sub.2 O).sub.4.sup.8+, they act as pillars, propping the clay layers apart to afford a pillared layered clay. Upon heating, these oligomers or polymers are converted to the metal oxide, thus preventing the collapse of the clay layers and thus pillaring the clay.
Smectite clays are a family of clays which include as its members montmorillonite, beidellite, nontronite, saponite, hectorite and sauconite. Of these materials beidellite, hectorite and saponite have been prepared synthetically. Saponite contains magnesium, aluminum and silicon and is represented by the formula EQU A.sub.x (Mg.sub.6)(Si.sub.8-x Al.sub.x)(O.sub.20)(OH.sub.4)
where A is a cation such as an alkali metal cation. In contrast, beidellite contains only silicon and aluminum and has the formula EQU A.sub.x (Al.sub.4)(Si.sub.8-x Al.sub.x)(O.sub.20)(OH.sub.4)
There are also reports that saponite can be prepared by substituting fluoride ions for the hydroxyl ions. Thus, U.S. Pat. No. 3,855,147 discloses a process for preparing a saponite material where a fraction of the hydroxyl groups are replaced by fluorides. Similarly U.S. Pat. No. 5,089,458 discloses a saponite derivative in which some of the magnesium has been replaced by a divalent metal ion and some of the hydroxyl groups have been replaced by fluorides. Finally, European Patent Publication 317,006A2 discloses the preparation of a saponite in which fluorides are used instead of hydroxyl.
In contrast to the above, applicant has prepared a fluorided beidellite. Applicant's process reacts a mixture containing reactive sources of aluminum, silicon, a cation salt and a fluoride source. This process differs from those disclosed in the art in that it is carried out at a pH of about 4 to about 9, at a low temperature and uses a fluoride source. Thus, applicant is the first to synthesize a fluorided beidellite clay.